Sunday, 17 February 2013

Woodcock on the wane

A long
wander through my local Wormley Woods coincided with the arrival of the latest
BTO newsletter. Woodcock was the connecting factor. I saw 2 Woodcock; one flushed by me and one by
a dog. Wormley Woods are very popular
with dog walkers and cyclists. Even the remote corner I explored had an
off-the-leash labrador tearing through it. I doubt I could find any significant
area of the wood without a squidgy tyre print or a doggy do. I later flicked through the BTO newsletter and
settled on the feature on the forthcoming Woodcock survey before shifting to
the BTO website. Woodcock have declined significantly
in recent decades. The old CBC recorded a 74% decline between 1968 and 1999. A quick look at the recent Atlas results
appear to show that Woodcock in Hertfordshire in particular have dropped away
sharply between the last two atlases, with the Broxbourne Woods complex
remaining a very small and tenuous toehold in the county. No-one really knows why they are declining but,
low and behold, recreational disturbance, the drying out of woodland,
overgrazing by deer and declining woodland management have been put forward as
possible causes.All four could apply to
Wormley Woods.No doubt the Woodland Trust and Natural
England are actively considering these issues at this very moment.

It is undoubtedly good that people get out and
enjoy wildlife-rich areas, including nature reserves, as human indifference to
wildlife is arguably its greatest threat. Yet disturbance to the very wildlife that we
are encouraging people to visit and enjoy is a real issue that can be subtle in
its effects.Research has
shown that disturbance can affect settling rates and patterns of breeding birds,
lower their productivity, and can result in reduced densities and delayed
breeding.

Studies of Nightjar (formerly present
in the local woods but now gone) have found a reduction in breeding densities
on sites heavily used by people and dogs.Increased nest failure due to daytime egg predation was found to be the
cause, particularly where nests are close to paths.The theory goes that as sitting birds are
flushed from nests, the eggs are exposed to predation, with the main predator
suspected to be crows.

The distribution of Woodlarks on
Dorset heaths was also found to be significantly affected by the presence of
people and dogs.Within sites with
recreational access, the probability of suitable habitat being colonized was
lower in those areas with greater disturbance; this was reduced to below 50% at
around eight disturbance events per hour. However, there was no effect of
disturbance on daily nest survival rates. Birds on sites with higher levels of
disturbance fledged more chicks (per pair) owing to a strong density-dependent
increase in reproductive output.However, in the absence of disturbance, overall productivity would be
34% higher.

Further afield, a fascinating study
on the island of Ouessant in France showed that visitors had a detrimental
impact on the survival of juvenile Chough simply by scaring them away from
feeding sites.Annual survival rates of
juveniles were found to be negatively correlated with the number of visitors
during August.The time spent foraging
by juveniles was 50% less than expected during this peak tourist month.Food for thought.Or not, if it happens to be August.

A grizzled old ecologist/birder, usually to be found roaming around the Lee Valley and occasionally further afield. Fortunate to be involved in the management of some of the UK's finest nature reserves and always looking for ways of improving them for birds.